Cooled motor for a paper shredder

ABSTRACT

A paper shredder motor cooling assembly having a paper shredder motor coupled to a fan shaft, an enclosure surrounding the paper shredder motor and having selected input and selected output vents to control airflow to the paper shredder motor, a fan coupled to the fan shaft, communicating with the selected input vents or the selected output vents; when the paper shredder motor is operating, the rotor shaft turns the fan to generate a differential air pressure between the selected input vents and the selected output vents, removing heat from the motor. A duty cycle of greater than 15 minutes is obtained. The fan can be coupled to the motor by speed increasing gearing, attached to the cutter blade assembly, such that the fan turns faster than the motor. The fan also can be attached to the motor shaft. An input fan and an output fan can be used.

BACKGROUND

1. Field of the Invention

The present invention relates to electric motors and more particularlyto paper shredders having electric motors with cooling apparatus.

2. Background Art

Consumer product satisfaction is driven at a particular product pricepoint by product safety, product reliability, and product longevity.This is particularly so in the field of consumer paper shredders, wherea shredder can endure excessive or rough wear despite the non-industrialfocus of the shredder product specifications. Such excessive or roughwear can, over time, degrade the reliability and longevity of theshredder product causing the consumer to become dissatisfied with theproduct. In some cases, repeated stresses on the moving parts of theshredder may cause part failure, leading to the expense of productrepair or replacement, a further decrease in satisfaction, or even lossof goodwill for the respective consumer in the paper shredder brand.Even marginally stressful moments of operation may in the aggregate taketheir toll on the operating machinery of the shredder.

One shredder part which can be vulnerable to mechanical and thermalstresses is the shredder electric motor, which can arise from, forexample, frequent starting, overloading, jamming, and continuous,beyond-rating use. Over time, the cumulative stresses faced by ashredder motor may lead to premature failure or poor performance. Acommon thread with these stressors is the heating effects of motorcurrent (I²R losses). Many sophisticated electronic controllers havebeen devised to reduce the effects of I²R losses upon motors. Complexmechanical cooling systems have been advanced for large motors, as well.However, in the sphere of fractional-horsepower electric motors, as usedin light- to medium-duty paper shredders, sophisticated electroniccontrollers and complex mechanical coolers can add prohibitive premiumsto the motor cost, and to the cost to consumers, reducing amanufacturer's market share. An inexpensive but efficacious coolingapparatus for paper shredder motors is needed.

SUMMARY

The foregoing need is met by cooling apparatus and methods for a motorfor a paper shredder. (To be filled in when Claims finalized)

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention disclosed herein are illustrated byway of example, and are not limited by the accompanying figures, inwhich like references indicate similar elements, and in which:

FIG. 1 is a perspective illustration of a shredder motor coolingapparatus including a fan cooler, in accordance with the teachings ofthe present invention;

FIG. 2 is a perspective illustration of the shredder motor coolingapparatus of FIG. 1, having overdrive gearing removed, in accordancewith the teachings of the present invention;

FIG. 3 is a perspective illustration of the shredder motor coolingapparatus of FIG. 1, having overdrive gearing removed, in accordancewith the teachings of the present invention;

FIG. 4 is a perspective illustration of the shredder motor coolingapparatus of FIG. 1, with perspective of the opposite end of FIG. 1;

FIG. 5 is a perspective illustration of another embodiment of a shreddermotor cooling apparatus including a fan cooler, in accordance with theteachings of the present invention;

FIG. 6 is a perspective illustration of the embodiment shredder motorcooling apparatus of FIG. 5, with perspective of the opposite end ofFIG. 5;

FIG. 7 is a graphical illustration of yet another embodiment of ashredder motor cooling apparatus using two fans, in accordance with theteachings of the present invention;

FIG. 8 is a graphical illustration of another embodiment of a shreddermotor cooling apparatus using a single fan, in accordance with theteachings of the present invention;

FIG. 9 is a graphical illustration of an embodiment of a shredder motorcooling apparatus as in FIG. 7, disposed in communication with a papershredder exterior, in accordance with the teachings of the presentinvention; and

FIG. 10 is a graphical illustration of an embodiment of a shredder motorcooling apparatus as in FIG. 8, disposed in communication with a papershredder exterior, in accordance with the teachings of the presentinvention.

Skilled artisans can appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to helpimprove the understanding of the embodiments of the present invention.In the figures, like numbers correspond to like elements.

DETAILED DESCRIPTION

Embodiments of the present invention can assist in reducing overheatingin a motor. In particular, selected embodiments can be used as aforced-air cooled motor, as may be used without limitation, to power ahome or office paper shredder.

FIG. 1 illustrates an embodiment of a shredder motor cooling apparatushaving shredder assembly 100, including motor 1, cooling fan 2,overdrive gearing 3, fan shaft 4, fan tube 5, first side plate 8, secondside plate 11, and shredder gearing housing 13. Perspective is that offirst side plate 8 forward, with one of shredder gearing exposed througha slot in housing 13. Motor 1 is disposed between first side plate 8 andsecond side plate 11. Shredder gearing housing 13 is disposed over gears(seen in part) coupled to the shaft (not shown) of motor 1, and isdisposed on the outer side of second side plate 11. Shredder gearing(not shown) is a reduction gearing, which also is coupled to shredderblade shaft (not shown). In assembly 100, overdrive gearing, which alsois speed increasing gearing, 3 is coupled to and motivated by theshredder blade shaft (not shown) and coupled to fan shaft 4. Fan shaft 4couples the shaft rotation through first side plate 8 to cooling fan 2.Fan tube 5 may be fitted tightly to motor 1 end, which motor 1 end mayhave selected ventilation holes (not shown) to admit the cooling air. Inoperation, motor 1 operates shredder gearing (not shown), which iscoupled to the shredder blade shaft (not shown). The shredder bladeshaft (not shown) can be coupled to overdrive gearing 3. Overdrivegearing 3 may be configured to turn shaft 4 and thus, cooling fan 2,providing a rotation of between about 4,000 RPM to about 10,000 RPM.Such a high-speed rotation can create a forceful current of air bycooling fan 2, which can be confined by fan tube 5 and directed to coolmotor 1. Such a fan configuration is capable of operating at a differentspeed from that of the motor 1, increasing cooling of motor 1 at a highthermal efficiency. Indeed, the produced efficiency may provide ashredder motor duty cycle of greater than 50%.

Referring to FIG. 2, shredder blade shaft assembly can be seen toinclude first driver shaft 7 and shredder blade shaft 6, both of whichare motivated by shredder gearing 12, which is partially seen throughcover 13. Shredder blades have been removed for clarity of presentation.Shredder blade shaft 6 can protrude through first side plate 8 and becoupled to overdrive gearing 3. Motor 1 can be affixed to second sideplate 11 and coupled to shredder gearing (partially shown through cover13). With fan tube 5 removed, selected tube vent holes may be seen inthe end of the can. Cooling fan 2 can be a simple axial fan, for lowcost. In FIG. 3, shaft bushings 9 (bearings) are illustrated on theouter side of first side plate 8. Protective coverings are illustratedas being in place on the shredder blade assembly.

FIG. 4 present an shredder assembly 100 from the vantage of second sideplate 11 forward, with shredder gearing housing 13 removed and shreddergearing 12 shown exposed. Protective coverings conceal the shredderblades in FIG. 4. Fan bezel 10 can be seen on the inner side of firstside plate 8. Fan bezel 10 is sized to admit fan shaft 4 therethroughand may provide additional support to high revolution speed of coolingfan 2.

FIG. 5 is an embodiment of shredder assembly 200 with forced cooling bycooling fan 2, without containment by fan tube 5. The perspective isthat of the first side plate 8 being forward. The operation andfunctionality of FIGS. 1-4 of shredder assembly 100 is substantially thesame in shredder assembly 200 without confinement of the air currentgenerated by cooling fan 2 within fan tube 5. FIG. 6 depicts shredderassembly 200 from the perspective of the second side plate 11 beingforward and gearing housing 13 being in place.

Turning to FIG. 7, still another embodiment of the present invention isdepicted. Motor 700 combined with cooling fans 720, 740 is shown, inwhich each of cooling fans 720, 740 can be enclosed within motor airchamber 722, 742, respectively. Motor 700 can be confined to a sealedcan 750, with limited paths for air flow with motor air chamber 722,742, and creating a defined heat transfer path within motor 700. Coolingfan 720 is disposed to be a forced air intake fan 720 coupled to theshaft 705 of motor 700. Cooling fan 740 is disposed to be a forced airoutlet fan 740 coupled to the shaft 705 of motor 700. Fans 720 and 740are positioned inline with motor rotor 710. When power is applied tomotor 700, rotor 710 rotates relative to stator 715 to translatemechanical power on shaft 705 from applied electrical energy. Fan 720insufflates air for cooling across motor 700. Fan 740 extracts air forcooling across motor 700. Either fan 720, or fan 740, or both, may beused. A portion of the mechanical power applied to shaft 705 is employedby fans 720, 740. Fans 720, 740 tend to rotate at the speed of shaft705, for example at about 3700 RPM. In selected embodiments, motor 700with inlet fan 720 and outlet fan 740 generate an energetic stream ofair directed from intake vent 724 to outlet vent 744, and through theregion of rotor 710 and stator 715, when energized. Sealed can 750 caninclude vent holes 755, 765 disposed on outlet side 724 of intake fan720, and disposed on intake side 744 of outlet fan 740, to providedirectional flow of air. Such forced air flow can be effective inremoving heat from rotor 710 and stator 715, increasing the duty cycleof motor 700 to nearly an order of magnitude greater than ordinary papershredder motors, for example, up to about 45 minutes. In selectedconfigurations, only one fan assembly may be used. In someconfigurations, a type of centrifugal fan can produce large volumes ofair because of a forced pressure differential across motor 700 fromintake fan 720 to outlet fan 740 created by at least one of fans 720,740 and guided by selected flow holes 755, 765. A centrifugal fan may beused for fan 720 and fan 740, although fans 720, 740 are not confined tosuch configurations. In other configurations, an axial fan can be used.In yet other configurations, a vane-axial fan may be configured toproduce an efficacious forced airflow by differential pressure. The heatremoved from motor 700 is increased over present paper shredder motorsdue to the increased forced air mass flow rate passing by the motorelements. The configuration of FIG. 7 may be disposed within theinterior of a paper shredder or in communication with the exterior ofthe paper shredder.

FIG. 8 illustrates that effective cooling also may be obtained by usinga single outlet fan 820 as a forced air outlet fan assembly for motor800. As before, shaft 805 of rotor 810 can provide the mechanical motiveforce for fan 820, derived from the electromagnetic interaction of rotor810 and stator 815. Motor 800 can be confined to an enclosure, e.g., asealed can, 850 with limited paths for air flow and for creating adefined air flow and a heat transfer path within motor 800. Vent holes855, 865 can be disposed to direct forced air flow from air intake side811 to air outlet side 842. Vent holes 855 provide for input cooling airinto motor 800 and manifold vent holes 865 provide for motor cooling airextraction into intake 845 of outlet fan 800. Fan 820 can be enclosedwithin motor air chamber 822, which can be communicatingly affixed toenclosure 850 to allow air flow through an end of the enclosure. Acentrifugal fan in such embodiments also can produce large volumes ofair because of a pressure differential across motor 800, created by fan820 and by guided vents, or flow holes 855, 865, from air intake side811 at one end of the enclosure to air outlet side 842 at the other endof the enclosure. However, and axial fan also may be used. Thisconfiguration may be disposed within the interior of a paper shredder orin communication with the exterior of the paper shredder. The heatremoved from motor 800 is increased over present paper shredder motorsdue to the increased forced air mass flow rate passing by the motorelements. Neither FIG. 7 nor FIG. 8 require a separate controller orpower supply for the forced air fans due to their integration with theshaft of the motor rotor. As with FIG. 7, an axial or a centrifugal fanassembly may be used.

Turning to FIG. 9, a motor 900, such as motor 700, can be seenpositioned in paper shredder housing 970, having an air input duct 975and an air output duct 985 disposed in housing 970. Air input duct 975can communicate with input vent holes 955; air output duct cancommunicate with output vent holes 960. In this configuration, theintake air manifold opening 930 is positioned on the exterior ofshredder housing 970, and communicates with air input duct 975,preventing internal shredder debris from being drawn into motor 900.Similarly, output air manifold opening 945 is disposed at the exteriorof shredder housing 970, and in communication with air output duct 985,so that the forced air from 900 does not cause the creation of a debriscloud by exhausting air onto the shreddant (not shown), which may be inor near housing 970. Air input duct 975 or air output duct 985, or both,may be positioned such that human access to input fan 920 or output 940is difficult. Screen 972, 973 may be placed over one or both externalopenings 930, 945. In certain embodiments, motor 900 is disposed in theinterior of shredder housing 970, without direct communication with theexterior of shredder housing 970. The heat removed from motor 900 isincreased over present paper shredder motors due to the increased forcedair mass flow rate passing by the motor elements. As with FIG. 1, anaxial or a centrifugal fan assembly may be used.

In FIG. 10, a single-fan motor 1000, similar to motor 800, is shown incommunication with exterior 1008 of paper shredder housing 1010. Similarto FIG. 9, the input air flow and output air flow is routed throughducts 1032, 1044 which are in communication with airflow manifoldopenings 1030, 1045. In FIG. 10, air is extracted from motor 1000. Itshould be noted that forced air fan 1040 which, in the example of FIG.10, is disposed on the outlet side of airflow, may instead be disposedon the input side of airflow. In the latter configuration, the forcedair fan may be positioned to insufflate air into the motor 1000 insteadof extracting air from motor 1000. In either case, a forced differentialair pressure causes a large volume of air to be moved past motor 1000.In still another embodiment, cooling fans may be located on the motorair input and the motor air output. The heat removed from motor 1000 isincreased over present paper shredder motors due to the increased forcedair mass flow rate passing by the motor elements. Air can be taken inthrough manifold opening 1030 and then through selected input vent holes1055. Air can be exhausted through selected output vent holes 1065 andout through manifold opening 1045. As with FIG. 7 or FIG. 8, an axial ora centrifugal fan assembly may be used.

The embodiments of the present invention disclosed herein are intendedto be illustrative only, and are not intended to limit the scope of theinvention. It should be understood by those skilled in the art thatvarious modifications and adaptations of the prevent invention as wellas alternative embodiments of the prevent invention may be contemplatedor foreseeable. It is to be understood that the present invention is notlimited to the sole embodiments described above, but encompasses any andall embodiments within the scope of the following claims.

What is claimed is:
 1. A paper shredder motor cooling assembly,comprising: a paper shredder motor coupled to a fan shaft; an enclosuresurrounding the paper shredder motor and having selected input andselected output vents disposed to control airflow to the paper shreddermotor; a fan coupled to the fan shaft and in communication with theselected input vents or the selected output vents, wherein when thepaper shredder motor is operating, the rotor shaft turns the fan togenerate a differential air pressure between the selected input ventsand the selected output vents, wherein heat is removed from the motor,and wherein a duty cycle of greater than 50% is obtained thereby.
 2. Thepaper shredder motor cooling assembly of claim 1, wherein the fan is aninput fan, insufflating air into the input vents and across the motor.3. The paper shredder motor cooling assembly of claim 1, wherein the fanis an output fan, extracting air through the output vents and across themotor.
 4. The paper shredder motor cooling assembly of claim 1, furthercomprising a blower input fan and a blower output fan each coupled tothe rotor shaft and in respective communication with the input vents andthe output vents.
 5. The paper shredder motor cooling assembly of claim1, further comprising: a reduction gearing coupled to the paper shreddermotor; a shredder blade shaft coupled to the reduction gearing; a speedincreasing gearing coupled to the shredder blade shaft; and the fanshaft is coupled to the speed increasing gearing, wherein the rotationalspeed of the fan is greater than the rotational speed of the papershredder motor.
 6. The paper shredder motor cooling assembly of claim 5,further comprising: a fan tube disposed between the fan and the selectedmotor inlet vents, the fan tube directing a forced air current to themotor from the fan.
 7. A paper shredder, comprising: a cutting bladeassembly having a shredder blade shaft; a motor having a rotor coupledto the cutting blade assembly; an enclosure enclosing the motor, theenclosure having first selected vent holes defining an input air path onone end and second selected vent holes defining an output air path onthe other end; and a fan assembly coupled to the rotor, disposed at anend of the enclosure, and in confined communication with the vent holes,wherein, when the motor is operating, the cutting blade assembly isurged to comminute shreddant and the fan assembly creates a pressuredifferential between the input air path and the output air path, andwherein the pressure differential causes air to be forced across themotor such that the motor is cooled.
 8. The paper shredder of claim 7,further comprising an air manifold opening coupled to the fan assemblywherein the enclosure is coupled to one of the input air path or theoutput air path, wherein the air manifold opening is in communicationwith the exterior of a paper shredder.
 9. The paper shredder of claim 7,further comprising an intake air manifold opening coupled to the inputair path and an output air manifold opening coupled to the output airpath, wherein the air manifold openings are in communication with theexterior of a paper shredder.
 10. The paper shredder of claim 7, whereinthe enclosure end having vent holes defining an input air path iscoupled to the fan assembly.
 11. The paper shredder of claim 7, whereinthe enclosure end having vent holes defining an output air path iscoupled to the fan assembly.
 12. The paper shredder of claim 7, whereinthe first enclosure end having selected input vent holes insufflatingthe motor through an input air path having an input fan.
 13. The papershredder of claim 12, wherein the second enclosure end has selectedoutput vent holes exhausting the motor through an output air path havingan output fan.
 14. The paper shredder of claim 10, wherein the secondenclosure end having selected vent holes defining an output air path iscoupled to a second fan assembly.
 15. The paper shredder of claim 7,wherein the fan assembly further comprises: a cooling fan blade; a tubedisposed between the cooling fan blade and an end of the enclosure; afan blade rotor affixed to the cooling fan blade; the fan blade rotorcoupled to a speed increasing gear assembly; and the speed increasinggear assembly coupled to the shredder blade shaft, wherein, when themotor rotor turns at a first speed, the shredder blade shaft turns at asecond speed, which assembly turns the fan rotor at a third speed,wherein the second speed is slower than the first speed and the thirdspeed is faster than the first speed, and wherein a forced air currentis blown onto an end of the motor enclosure, cooling the motor.
 16. Apaper shredder, comprising: a shredder enclosure; an air intake manifoldformed into the shredder enclosure; a motor coupled to a shreddercutting blade assembly and to the air intake manifold; an intake fandisposed between air intake manifold and selected inlet vents on theshredder motor, operating to insufflate a high volume of air into themotor for cooling, wherein the fan is coupled to the motor.
 17. Thepaper shredder of claim 16, wherein the fan is directly coupled to themotor.
 18. The paper shredder of claim 16, wherein the fan is coupled bya speed increasing gearing to the motor.
 19. The paper shredder of claim17, further comprising: an air outlet manifold formed into the shredderenclosure and coupled to selected outlet vents on the motor, disposed toexhaust a high volume of air from the motor for cooling, wherein theinlet fan is affixed to a shaft of the motor.
 20. The paper shredder ofclaim 19 further comprising: an outlet fan disposed between air outletmanifold and selected outlet vents on the shredder motor, disposed toexhaust a high volume of air from the motor for cooling, wherein theoutlet fan is affixed to the shaft of the motor.